1. Field of the Invention
The present invention relates to a loop diagnosis system and method for disk array apparatuses, and more particularly to a loop diagnosis system and method for disk array apparatuses using an FC-AL (Fibre Channel-Arbitrated loop) interface disk.
2. Description of the Related Art
Along with the development of the information technology (IT) environment in recent years, the role of storage units in computer systems is taking on ever increasing importance, and the requirements for their performance, reliability and capacity also keep on increasing in stringency. In disk array apparatuses, these requirements are met by conforming the interface with the host to the FC-AL [Fibre Channel-Arbitrated Loop: a loop prescribed by ANSI (American National Standards Institute) X3.272-199x Rev 5.7 Aug. 22, 1997] or mounting the apparatus with an FC-AL interface disk.
If a loop abnormality, such as a link-down, occurs in an FC-AL (hereinafter to be referred to simply as a “loop”) to disturb the loop state, processing on any other normal disk connected to the loop may be affected and become no longer able to function normally. In order to bring back the loop into a normal state, any faulty part should be removed from the loop, but if the loop abnormality is intermittent, complex loop diagnosing will be needed to pinpoint the faulty part, and in a modern disk array apparatus in which many disks are connected in a loop, it takes a long time to identify and remove the faulty disk.
One of such disk array apparatuses is disclosed in the Japanese Patent Application Laid-open No. 1999-353126 (Reference 1). According to the technique disclosed in Reference 1, the troubled loop is once cut off, and disks in the disk array apparatus are connected to the initiator host one by one to locate the fault. The faulty disk, as it is identified, is removed from the loop. This facilitates the faulty disk and serves to reduce the time taken to identify it.
Another such disk array apparatus is disclosed in the Japanese Patent Application Laid-open No. 1999-305944 (Reference 2) and the Japanese Patent Application Laid-open No. 1999-306644 (Reference 3). Reference 2 discloses an arrangement in which the link state is indicated by turning a lamp on when a link-down occurs and turning it off at the time of a link-up. Reference 3 discloses a technique by which the faulty disk is diagnosed after it is separated from the loop.
However, the technique disclosed in Reference 1 involves a problem that processing on normal disks is interrupted during the attempt to identify the faulty disk. There is a further disadvantage that, if the number of disks connected to the loop increases reflecting an expanded capacity of the disk array apparatus, the time taken to diagnose the loop will be further extended, and so will be the duration of the interruption of normal disk processing. Nothing to solve these problems is proposed in either Reference 2 or 3.